Whisk the egg yolks in a medium bowl until smooth, about 1 minute. Gradually whisk in the sugar, and continue whisking until the mixture is thick and considerably lighter in color, about 2 minutes. Park by your cooktop.
Heat the half-and-half, nutmeg, and grains of paradise in a medium saucepan over medium-high heat and whisk occasionally until the mixture reaches 165 degrees F, about 7 minutes. Remove from the heat and whisk the egg mixture constantly while slowly ladling about a quarter of the hot dairy into it. Then, reverse the process and whisk the dairy while adding all of the egg mixture back into the saucepan. Congratulations, you've made a custard.
Return the custard mixture to medium heat and stir frequently until it reaches 175 to 180 degrees F, about 3 minutes. Meanwhile, place a second medium bowl inside a large bowl filled with ice and set a fine-mesh sieve over the bowl.
Remove the saucepan from the heat, pour the custard through the sieve into the bowl, then stir in the bourbon, rum, sherry, and vanilla. Continue stirring until the mixture is cool. Chill thoroughly. Consume immediately or move to a sealable container and refrigerate for up to two weeks.
To serve, grate on a little nutmeg if you like, and enjoy…responsibly, of course.